In recent years, there has been an increasing demand for formation of a toner having a small particle size as well as high image quality. In general, in the formation of a toner having a small particle size, a process including the steps of jetting a jet air containing a powder raw material from a venturi nozzle, and pulverizing a powder raw material by an impact to an impact member, and further by a secondary impact to a wall surface has been carried out, and various studies have been made in the aim of improving pulverization efficiency. In connection to those relating to the shapes of the impact members, those that are arranged perpendicular to or slanted to the direction of the jet stream, having a flat shape (JP-A-Showa-57-50554 and JP-A-Showa-58-143853), a conical shape (JP-A-Hei-1-254266 and JP-A-Hei-11-70341), a spherical shape (JP-A-Hei-8-117633), and the like have been disclosed. On the other hand, as to the venturi nozzle, those having an improved shape in a throat part (JP 2000-140675 A) have been disclosed. However, in these conventional methods, a fine powder having an even smaller particle size than the desired particle size is generated in a large amount, thereby lowering production efficiency of the toner. Therefore, its improvement has been desired.